A green and efficient procedure for the preconcentration and determination of cadmium, nickel and zinc from freshwater, hemodialysis solutions and tuna fish samples by cloud point extraction and flame atomic absorption spectrometry

Deep eutectic solvent-based simultaneous complexation and preconcentration of nickel in Antarctic lake water samples for determination by flame atomic absorption spectrometry

This study presents a simple, sensitive, and accurate method for the determination of nickel by flame atomic absorption spectrometry (FAAS). Prior to instrumental measurement, a deep eutectic solvent-based simultaneous complexation and preconcentration (DES-SCP) method was used to preconcentrate nickel from aqueous solution into measurable quantities. The efficiency of the extraction method was enhanced by forming a non-ionic complex of nickel using dithizone as ligand. By mixing the ligand with the DES extractant, simultaneous complexation and preconcentration of nickel were achieved in a single step. Under optimum conditions of the extraction method, the limit of detection (LOD) and the limit of quantification (LOQ) values were found to be 2.4 and 8.0 ng/mL, respectively. With respect to direct FAAS measurement, the developed method enhanced the sensitivity of nickel determination by about 169 folds. The accuracy and applicability of the developed method were evaluated by performing spike recovery experiments with lake water sampled from Antarctica. Satisfactory recovery results in the range of 94.0-113.7% were recorded and this validated the developed method as an efficient and green alternative for nickel determination.

Ultrasound-assisted deep eutectic solvent-based liquid-liquid microextraction for simultaneous determination of Ni (II) and Zn (II) in food samples

A new approach was developed for the simultaneous pre-concentration and determination of Ni (II) and Zn (II) in food samples. This method is based on ultrasound-assisted liquid-liquid micro extraction using hydrophobic deep eutectic solvent (DES) and 1,10-phenanthroline as chelating agent. The effect of several parameters, such as pH, selection and volume of DES, amount of chelating agent, time of sonication and centrifugation, was studied. Under optimized conditions, the developed procedure offered exceptional sensitivity and linearity. The limit of detection was approximately 0.029 µg/Kg and 1.5 µg/Kg for Ni (II) and Zn (II), respectively. The proposed method was applied for the pre-concentration and determination of Ni (II) and Zn (II) in hydrogenated edible oils, fishes, and milk samples. The results of this study were compared with reported methods in the literature revealing its advantages.

Determination of nickel in daphne tea extract and lake water samples by flame atomic absorption spectrophotometry with a zirconium-coated T-shaped slotted quartz tube-atom trap and photochemical vapor generation sample introduction

Nickel determination is important because of its use in many industrial areas and its negative effects on human health. In this study, an ultraviolet-based photochemical vapor generation (UV-PVG) setup was combined with a T-shaped zirconium-coated slotted quartz tube-atom trapping (T-SQT-AT) apparatus to boost the sensitivity of a flame atomic absorption spectrophotometer for nickel determination. Nickel was separated from the sample matrix by converting it into its volatile species prior to online preconcentration by trapping on the zirconium-coated T-SQT inner surface. Analytical performance was maximized by optimizing all variable conditions. The limit of detection (LOD) and limit of quantification (LOQ) were found as 10 and 33 µg/L, respectively. Daphne tea and lake water samples were analyzed under optimum conditions, and there was no detectable nickel in the samples. For this purpose, spiking experiments were carried out for the samples in order to evaluate the applicability and accuracy of the method. The percent recovery values calculated for the two samples spiked at three different concentrations ranged between 90 and 112%. To our best knowledge, this is the first study in literature where UV-PVG was combined with T-SQT-AT for the determination of nickel in daphne tea and lake water samples prior to FAAS determination.

Ultrasound-Assisted Ionic Liquid Microextraction for Preconcentration of Cadmium in Water, Vegetables and Hair Samples Prior to FAAS Determination

Background::

Cadmium (Cd2+) is considered to be one of the most important hazardous heavy metals due to its toxicity for living organisms at low concentration levels. Therefore, the estimation of trace Cd2+ in different types of various samples is a very important objective for chemists using effective methods. In the present work, a novel, green, easy and fast ultrasoundassisted ionic liquid-dispersive liquid phase microextraction technique (UA-IL-DLPME) was developed to preconcentrate and determine trace quantities of cadmium (Cd2+) ions from real samples, prior to detection by FAAS.

Methods:

The proposed technique is based on utilization of ionic liquid (IL) (1-hexyl-3- methylimidazolium tris(pentafluoroethyl)trifluorophosphate [HMIM][FAP]) as an extraction solvent for Cd2+ ions after complexation with 2-(6-methylbenzothiazolylazo)-6-nitrophenol (MBTANP) at pH 7.0. The impact of different analytical parameters on the microextraction efficiency was investigated. The validation of the proposed procedure was verified by the test of two certified reference materials (TMDA-51.3 fortified water, SRM spinach leaves 1570A) applying the standard addition method.

Results:

In the range of 2.0-200 μg L−1, the calibration graph was linear. Limit of detection, preconcentration factor and the relative standard deviation (RSD %, 100 μg L-1, n=5) as precision was 0.1 μg L-1, 100 and 3.1%, respectively.

Conclusion:

Green UA-IL-DLPME method was developed and applied to preconcentrate and determine trace quantities of Cd2+ in real water, vegetables and hair samples with satisfactory results.

Deep Eutectic Solvent Based Air Assisted Ligandless Emulsification Liquid-Liquid Microextraction for Preconcentration of Some Heavy Metals in Biological and Environmental Samples

In this study, a deep eutectic solvent (DES) based on air-assisted ligandless emulsification liquid-liquid microextraction method (DES-AA-LL-ELLME) was considered for preconcentration and extraction of some metals (Cd, Ni, Pb and Cu). A 1:1 mixture of the synthesized DES and triethylamine was added as an extractant to extract metal ions in the absence of chelating agent. Tetrahydrofuran as the aprotic solvent provided a turbid state. To disperse the aggregated DES droplets into the aqueous phase, air-assisted was performed. The influence of several effective parameters was monitored. Under optimum conditions, limits of detection were found in the range of 0.31-0.99 µg L^-1 with preconcentration factor from 67 to 69. The relative standard deviation (n = 10) was in the range of 2.1%-3.1% for all analytes. This procedure was applied to determine some metals in both biological and environmental samples with appropriate recoveries about 98.7%-106%.

Butan-1-ol as an extractant solvent in dispersive liquid-liquid microextraction in the spectrophotometric determination of aluminium

Determining aluminium ions at μg L^-1 scale currently requires either costly analytical techniques such as inductively coupled plasma, and/or graphite furnace atomic absorption spectrometry. Dispersive liquid-liquid microextraction (DLLME) is designed to promote separation and preconcentration, thus making it possible to determine the analyte of interest without significant matrix influence. This study was aimed at the development of a spectrophotometric method to determine Al³⁺ after microextraction of its complex with quercetin. Butan-1-ol was used as a novel extractant solvent in the DLLME process. The parameters influencing complexation and microextraction, such as the amount of quercetin and volume of extractant were evaluated by univariate analysis. In optimised conditions were estimated for the proposed method: linear range from 7.5 to 165.0 μg L^-1, LOD of 2.0 μg L^-1, and LOQ of 7.0 μg L^-1. The accuracy was checked by applying the proposed method to water (NIST SRM-1643e) and rice flour (NIST SRM-1568c) certified reference materials and spike-and-recovery trials with distinct samples (mineral water, green tea, thermal spring water, contact lens disinfecting solution, saline concentrate for hemodialysis and urine).

A Green and Efficient Method for the Preconcentration and Determination of Gallic Acid, Bergenin, Quercitrin, and Embelin from Ardisia japonica Using Nononic Surfactant Genapol X-080 as the Extraction Solvent

A simple cloud point preconcentration method was developed and validated for the determination of gallic acid, bergenin, quercitrin, and embelin in Ardisia japonica by high-performance liquid chromatography (HPLC) using ultrasonic assisted micellar extraction. Nonionic surfactant Genapol X-080 was selected as the extraction solvent. The effects of various experimental conditions such as the type and concentration of surfactant and salt, temperature, and solution pH on the extraction of these components were studied to optimize the conditions of Ardisia japonica. The solution was incubated in a thermostatic water bath at 60°C for 10 min, and 35% NaH₂PO₄ (w/v) was added to the solution to promote the phase separation and increase the preconcentration factor. The intraday and interday precision (RSD) were both below 5.0% and the limits of detection (LOD) for the analytes were between 10 and 20 ng·mL^-1. The proposed method provides a simple, efficient, and organic solvent-free method to analyze gallic acid, bergenin, quercitrin, and embelin for the quality control of Ardisia japonica.

A new thiourea derivative [2-(3-ethylthioureido)benzoic acid] for cloud point extraction of some trace metals in water, biological and food samples

2-(3-Ethylthioureido)benzoic acid was prepared and characterized by electronic spectrum, elemental analysis, Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectrum and mass spectrum. The produced ligand was applied for the preconcentrative of Fe³⁺, Co²⁺, Cu²⁺ and Zn²⁺ in aqueous samples by cloud point extraction methodology. Triton X-114 was used as extractant. Experimental parameters that may affect the extraction process were examined and optimized; such as pH, ligand and triton concentrations, type of diluting solvent, extraction temperature and ionic strength. The calibration curves were linear upto 500μgL^-1 for Fe³⁺, Cu²⁺ and Zn²⁺ and upto 200μgL^-1 for Co²⁺. The achieved detection limits were 1.5, 0.23, 0.71 and 0.35μgL^-1 for Fe³⁺, Co²⁺, Cu²⁺ and Zn²⁺ respectively. The accuracy was established by analysis of certified reference materials (Seronorm whole blood L2 and ZCS ZC85006 Tomato). The proposed procedure was used for preconcentration of these metal ions in water, biological and food samples prior to their determination by flame atomic absorption spectrometry.

Selective Micellar Extraction of Ultratrace Levels of Uranium in Aqueous Samples by Task Specific Ionic Liquid Followed by Its Detection Employing Total Reflection X-ray Fluorescence Spectrometry

A task specific ionic liquid (TSIL) bearing phosphoramidate group, viz., N-propyl(diphenylphosphoramidate)trimethylammonium bis(trifluoromethanesulfonyl)imide, was synthesized and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, and IR spectroscopies, elemental (C H N S) analysis, and electrospray ionization mass spectrometry (ESI-MS). Using this TSIL a cloud point extraction (CPE) or micelle mediated extraction procedure was developed for preconcentration of uranium (U) in environmental aqueous samples. Total reflection X-ray fluorescence spectrometry was utilized to determine the concentration of U in the preconcentrated samples. In order to understand the mechanism of the CPE procedure, complexation study of the TSIL with U was carried out by isothermal calorimetric titration, liquid-liquid extraction, ³¹P NMR and IR spectroscopies, and ESI-MS. The developed analytical technique resulted in quantitative extraction efficiency of 99.0 ± 0.5% and a preconcentration factor of 99 for U. The linear dynamic range and method detection limit of the procedure were found to be 0.1-1000 ng mL^-1 and 0.02 ng mL^-1, respectively. The CPE procedure was found to tolerate a higher concentration of commonly available interfering cations and anions, especially the lanthanides. The developed analytical method was validated by determining the concentration of U in a certified reference material, viz., NIST SRM 1640a natural water, which was found to be in good agreement at a 95% confidence limit with the certified value. The method was successfully applied to the U determination in three natural water samples with ≤4% relative standard deviation (1σ).

Effects of chlorine on the volatilization of heavy metals during the co-combustion of sewage sludge

To clarify the volatilization of heavy metals (Cu, Ni, Pb, and Zn) in sewage sludge during co-combustion in cement kiln, effects of addition and types of four chlorides and temperature on the volatilization of heavy metals in raw meal with 25wt.% sewage sludge were investigated. The results showed that the volatilization of Cu, Ni, and Pb increased significantly with increase of chlorides addition, while no obvious change in the volatilization of Zn was observed. The effectiveness of chlorides on the volatilization of heavy metals depended on their release capacity of chlorine radicals and the chlorine combined capacity of heavy metals. Higher calcination temperature resulted in dramatically increase in the volatilization of heavy metals due to easier formation of volatile heavy metal chlorides. The results will provide a guideline for co-combusting heavy metals contained solid wastes in cement kiln on the basis of security.

On-line Ultrasound-Assisted Dispersive Micro-Solid-Phase Extraction Based on Amino Bimodal Mesoporous Silica Nanoparticles for the Preconcentration and Determination of Cadmium in Human Biological Samples

On-line ultrasound-assisted dispersive micro-solid-phase extraction (USA-DμSPE) has been developed for preconcentration and separation of trace amounts of Cd(II) ions in 0.5 mL of human biological samples. In a syringe with a nylon membrane, new synthetic bulky amino bimodal mesoporous silica nanoparticles (NH2-UVM7) were dispersed as a nanoadsorbent in 5 mL of diluted serum sample (1:10), and after ultrasonic shaking, the liquid phase was separated from the solid phase. At the optimized pH, the chemical and physical adsorption of cadmium ions occurred, respectively, based on complexation with amine groups of UVM7 (Cd:NH2-UVM7) and silica nanoparticles. The analyte was then back-extracted from the sorbent with nitric acid solution (0.2 M), and its concentration was determined by electrothermal atomic absorption spectrometry (ETAAS). Under the optimized conditions, the linear range, limit of detection (LOD), and preconcentration factor (PF) were obtained as 0.01-0.56 μg L(-1), 0.002 μg L(-1), and 25, respectively. The adsorption capacity of NH2-UVM7 was found to be 108.6 mg g(-1) of cadmium. The validation of the methodology was performed by the human standard reference material (HSRM).

Development of cloud-point extraction method for preconcentration of trace quantities of cobalt and nickel in water and food samples

A new, efficient, and sensitive cloud point methodology was developed for preconcentration of trace quantities of cobalt and nickel in water and food samples.

Simultaneous preconcentration of uranium and thorium in aqueous samples using cloud point extraction

Simultaneous cloud point extraction of uranium and thorium in aqueous samples with the highest reported extraction efficiencies and preconcentration factors.

Application of Cloud Point Extraction for Cadmium in Biological Samples of Occupationally Exposed Workers: Relation Between Cadmium Exposure and Renal Lesion

Cadmium (Cd) level in blood and urine of soldering iron workers (n=49) and 41 matched healthy controls has been assessed. Cloud point extraction was employed for preconcentration of Cd. The Cd ions formed hydrophobic complex with 9,10-phenanthraquinone monoethyl thiosemicarbazone that was extracted by surfactant-rich phases in the nonionic surfactant Triton X-114. The surfactant-rich phase was diluted with 1 M HNO3 in methanol prior to its analysis by graphite furnace atomic absorption spectrometry. The parameters affecting the extraction efficiency of the proposed method, such as solution pH, amount of complexing agent, surfactant concentration, temperature, and incubation time, were optimized. Under the optimum experimental conditions, the detection limit and the enrichment factor were 0.04 μg L(-1) and 61, respectively. Relative standard deviation of 10 μg L(-1) Cd was less than 3.0%. The accuracy of the method was examined by analysis of certified reference materials. It was observed that soldering iron workers are liable to Cd overload as indicated by higher levels of Cd in blood and urine when compared with the controls. This exposure may lead to kidney damage indicated by elevation of urinary excretion of both N-acetyl-β-D-glucosaminidase and β2-microglobulin.

A new coprecipitation method without carrier element for separation and preconcentration of some metal ions at trace levels in water and food samples

A new simple and sensitive preconcentration, separation and environmentally friendly method based on carrier element free coprecipitation (CEFC) was developed using 4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (APSAL) as a new organic co-precipitant to precipitate Cr(3+), Cu(2+), Fe(3+), Pb(2+) and Zn(2+) ions from water and food samples. The levels of the studied elements were detected by flame atomic absorption spectrometry (FAAS). The impact of several analytical parameters, such as pH, sample volume and coprecipitant amount as well as centrifugation rate and time was investigated to recover the examined metal ions. The influence of matrix ions was also tested, and no interferences were observed. The recovery values of the analyte ions were calculated and found to be in the range of 95-101%. The detection limits, corresponding to three times the standard deviation of the blank (N=10), were found to be in the range of 0.2-1.2 μg L(-1). The relative standard deviation (RSD) was calculated to evaluate the precision of the proposed method and was found to be ≤5.0%. The calculated preconcentration factor was 100. The proposed method was successfully applied to separate and preconcentrate trace amounts of ions in several water and food samples. To confirm the accuracy and validate the proposed method, certified reference materials were analyzed with satisfactory results.